Relay-generator or relay-dynamo and its application to traction



July 27, 1937. R. E. GRATZMULLER I 2,037,948

RELAY GENERATOR OR RELAYVDYNAMO AND ITS APPLICATION TO TRACTION FiledMar-ch 12, 1934 2 Sheets-Sheet 1 July 27, 1937. L.. R. E. GRATZMULLER 2,087,948

RELAY GENERATOR OR RELAY DYNAMO AND ITS APPLICATION TO TRACTION Fil'ed March 12, 1934 2 Sheets-Sheet 2 manta:

LOUIS REN EUGENE GRATZMULLER fiymf l okw. M M a Patented July 27, 1937 UNITED STATES PATENT OFFICE RELAY-GENERATOR OR RELAY-DYNAMO AND ITS APPLICATION TO TRACTION Louis Rene Eugene Gratzmuller, Paris, France 8 Claims.

This invention resides in a device for the excitation of main dynamos, used either as motors or generators, with a continuous current by relay dynamos, and it can be. applied to electric traction for driving or braking the driving axles or braking thevehicle with recuperation. The excitation uses relay or exciter dynamos, of which the operation should be first of all described and explained in an elementary manner. The dynamos or exciting relays are excited under three potentials.

The present invention is an improvement on the device disclosed in my copending application, Serial No. 599,559, filed March 17, 1932.

With these and other objects in view as will appear hereinafter, the. present invention resides in the parts, combinations and circuit connections set forth in the following specification and recited in the appended claims.

In order to make the invention more clearly understood, there is shown in the accompanying drawings means for carrying the same into practical effect without limiting the improvements in their useful applications to the particular constructions which, for the purposes of explanation, have been made the subject of illustration.

Figure l is a schematic view of a dynamo according to the present invention.

Fig. 2 shows a chart containing a curve of the excitation characteristics or electromotive power 0 characteristics of the dynamo of the present invention as a function of the ampere-turns of the excitation.

Fig. 3 is a schematic view of modified form of the present invention.

35 Fig. 4 is a schematic view illustrating the use of the dynamo of the present invention as the excitation means of a main dynamo.

Fig. 5 is another schematic view showing a modification of the circuit in which the dynamo 4.0 of the present invention is utilized as a means of excitation.

Fig. 6 is a schematic View showing a modification of the circuit in which the exciting relay dynamo is arranged in a branch of the circuit 45 including the exciting winding.

Fig. '7 is another schematic view showing a circuit in which two main dynamos are excited by a single relay dynamo.

The dynamo forming the object of this inven- 0 tion will be termed a relay dynamo in the following description. This term is selected because of the analogy between applicants dynamo and an ordinary electromagnetic relay which will be explained hereinafter.

55 As shown in Fig. 1 of the drawings, a relay dynamo is schematically represented and includes an armature AB, a series field winding K and an exciting winding 1 connected between two terminals T and G. These terminals may be connected to the main conductors of a power sup-ply network.

As indicated in Fig. 1, the exciting winding 1 is adapted to be energized by the algebraic sum of three separate voltages. For this purpose, the winding '1 is included in an excitation circuit which is connected across the armature AB. The 10 excitation circuit also includes a resistance R7 and serially connected generators Us and 12b.

The voltage vb produced by generator Db may be adjusted by varying the current flowing through the. exciting winding cd. This voltage 15 ch may be impressed on the circuit including the winding 1 by means other than the generator shown. For instance, a battery may be used or the circuit may be connected to the mains of a power line. In any event, this voltage 'Ub will be termed the. adjustable voltage.

Voltage 173,, is produced in a small generator Us. which is driven at a constant speed and in which the non-saturated part of the magnetic circuit is used. Excitation of generator Us. is effected by a winding 2 1 connected in series with the armature AB and through which the. dynamo current i flows. This voltage u is termed the compounding voltage.

The third voltage acting on the exciting circuit including winding 1 is the voltage CAB across the armature AB. This voltage is termed the shunt voltage.

When the relay dynamo is operating as a generator, it is assumed that it generates the current i as represented by the broken line arrow 2'. In its output circuit, there may be between T and G a voltage V:VT-VG, such as the voltage of the network mains to which T and G are connected, a resistance, a self-inductance and the like, and/or the voltage V of any current-receiving devices comprising resistance, self-inductance, which voltage may be constant or variable within certain limits.

In order to illustrate the characteristics of the 5 magnetic circuit as a relation between the electromotive force eAB of the armature and the magnetizing ampere-turns, there is shown in Fig. 2 a curve resulting from the plotting of the values of eAB as ordinates against the magnetizing ampere-turns or the excitation current iv for a given speed of the armature as abscissa. The total resistance of the circuit A1-B, including the winding 1 and the armature AB, should be adjusted so that the curve obtained by plotting the ivR drop of this circuit as ordinates against the magnetizing ampere-turns or excitation current is will coincide with the. straight portion of the curve shown in Fig. 2. This adjustment of the resistance can be efiected by the addition to the circuit of a resistance R7, which may be fixed or variable.

It has been supposed that the maximum value of the voltage QAB on the straight part of the characteristics curve is greater than the voltage which is necessary for producing the excitation current i7 which is itself necessary in the exciting winding l for generating the voltage @AB and obtaining the current i in the armature which is proportional to voltage 'Ub with any value of V in certain limits and with any self-inductances in the eifective circuit, as briefly explained hereinafter.

Finally, in generating operation of the main dynamo, the voltages or; and 6A1; are arithmetically added together in the operation of the machine as a generator and the voltage Ua is subtracted from the sum of the two other voltages, so that the total excitation voltage is:

(The setting of a symbol between two strokes indicates that the values are absolute.)

An explanation of the operation will now be given for the case in which it is supposed, for simplification, that either any slow variation of the circuit parameters or a nearly stationary working condition occurs. In this case the electromotive self-inductance forces are small with respect to the ohmic drops and the sense of the phenomenon has not been altered through neglecting the same.

If vn=11t=0 or ii 'Ub--'l)a:0, producing the same effect, the shunt excitation alone remains, and therefore whatever i7 may be in the winding 1:

The electromotive force cm; is constant and the point M which represents the same is steady on the characteristics curve.

If, on the contrary, Db-Du slowly increases from the value 0, the voltage in the magnetizing circuit 1 increases (Fig. 2) at every moment by:

The current is in the winding 1 increases and with it the voltage can; the point M moves and the current 1' increases. But, then, a/ increases, the difference /'Ul2'Ua/ diminishes and as soon as va vb at the moment t, the current i7 becomes constant and the point M becomes steady in its position at the moment it.

If, on the contrary, the difference /Ub//Ua/ diminishes from the value 0 in a continuous manner, the point M moves in contrary direc tion and i7 diminishes. As soon as /Ul2/=/'Ua/ the point M becomes steady. Now

hmzK i/ K1 being a constant, so that at the limit:

which relation was to be demonstrated.

It will be noted that at every instant the E. M. F. elm is equal to the ohmic drop in the field winding. On the contrary, the diiference ('Ub)-('l)a) produces an increase or decrease in the field current L7 in the exciter by pushing the point M upwards or downwards (Fig. 2). Owing to this difference, the winding 1 plays the part of a sort of relay controlling the increase or the decrease of the current i1 and of the voltage of the dynamo AB to obtain finally the armature current i proportional to the separate regulatable voltage 21s. This arrangement is analogous to that of an electromagnetic relay, the winding of which is excited by a difference of two voltages to eifect a short circuit or introduce a resistance arranged in the field circuit to cause an increase or decrease by this operation of the voltage of the excited dynamo. The dynamo of the present invention is properly termed a relay dynamo.

It is also easy to conceive that if the armature 'Ub is driven proportionally to a speed to and excited by a constant current i, then Ub Kbw and, therefore, KiizKbw and i Kw, K being always a constant.

The current 2' is then proportional to the speed no. It is to be seen that if the dynamo AB is driven at the same speed to as the speed of the sub-exciter dynamo b, or at a speed which is proportional thereto, it will then produce an output which will be proportional to the speed to and, therefore, approximately a torque remaining constant if the dynamo feeds, for instance, against the constant voltage V of the network mains.

When running as a motor, the current i changes its sign as shown in full line arrows in Fig. 1 and the voltage in of the generator Us. is reversed and becomes The sign of Pb must be changed or the direction in which the voltage 72b is introduced into winding I must be reversed.

Through the same reasoning as for running as a generator it could be seen that i is still proportional to '01) when running as a motor.

In like manner as for running as a generator. if the exciter dynamo 'Ub is driven at a variable speed and excited with constant current, the main current i will be proportional to the speed w.

The arrangement shown in Fig. 3 can be used for motor operation as well as generator operation.

Because of the transitory working conditions, the dynamo AB can be advantageously provided with an exciter winding K excited in direct series by the current i of the main armature (Figs. 1 and 3) for limiting the over-intensities which are due to the sudden variations of V or of r, i. e., the resistance in the output circuit of the dynamo. The ampere-turns of the winding K must increase the exciter fiux when running as a motor and diminish the same when running as a generator.

It is obvious that the same result may be obtained by arranging the voltages Us, '01), 6A3 not in a single winding, but in separate excitation windings, for instance, two of said voltages on one of the windings and the third voltage on another winding.

In Fig. 3 of the drawings there is shown a schematic diagram in which the armature AB is excited by a winding 8 in addition to the winding 1. In the arrangement shown, winding 1' is connected across the armature AB as in the case of Fig. l. The circuit containing winding I and armature AB includes a generator 'Ub excited by winding c.d. for producing an adjustable voltage 013- In Fig. 3 the voltage 0.1, which is proportional to the armature current i is replaced by the am pare-turns produced by current i flowing through winding 8. Thus, it can be said that the voltage feeding winding 3 is a part of V--AB and that the so-called compounding voltage ea is replaced. by a compounding exciting winding. In fact, the proportional ampere-turns of i in the winding 1 are replaced by ampere-turns in winding 8 which are proportional to i.

The relay dynamo of the present invention may be advantageously used as an exciter dynamo and in Fig. 4: there is shown diagrammatical- 1y how connections should be made when so used. In this instance, a main dynamo having an armature XY and. exciter windings K and H is con nected by terminals T and G to the mains of a network. Winding K is connected in series with the armature XY. Winding H is energized by the armature of the relay dynamo AB' driven at constant speed and positioned in the electric circuit closed on H.

As shown, the armature AB' of the relaydynamo is excited by winding 1 to which voltages ems, '01: and us are applied in series as in the case of the dynamo AB of Fig. 1.

Voltage vb, which is. adjustable, is generated, for instance, in the sub-exciter dynamo Ub excited by means of the winding ed with an adjustable current. The speed of b is constant or variable and it is, for instance, proportional to the speed of the wheels of a vehicle in the case of the use of the dynamo KY for traction purposes.

The voltage on is developed in the armature of the sub-exciter dynamo 0a, the magnetic circuit of which is non-saturated. Dynamo vs is driven at a constant speed and excited by the winding e f in which the current i of the main armature The theory is obviously the same as in the case of the dynamo in Fig. 1, the straight part of the curve of the characteristics of AB being used alone and coinciding with the straight ohmic drop of the excitation circuit 1 of AB'. Instead of using the relay dynamo of Fig. 1, that of Fig. 3 could be used in the same manner.

In Fig. there is shown a modification in which both exciting windings H and K are serially connected with the armature XY of the main dynamo. The armature. AB' of a relay dynamo simi lar to that appearing in Fig. l is disposed in an electric circuit closed by a shunt p on the winding H. The armature AB can be placed in the branch H (Fig. 5) or in the branch p (Fig. 6).

For starting and for running with direct excitation, the contactors 4 and 5 are closed and contaotors 6 and 9 are open. With these connections, both windings H and K are energized by the current flowing through the armature XY only. When it is desired to operate the main dynamo as a generator and excite winding H by means of the relay dynamo A'B' the contactor 5 is opened so that the current i of the main armature XY flows through the armature A'B of the relay dynamo. The contactor 4, by which the exciting winding e f of the sub-exciter dynamo in had been shortcircuited, is then opened. Next, the contactor 9 is closed to complete the circuit including the winding 1 and then exciting winding 0 d is energized to excite the sub-exciter dynamo Ub- Finally, contactor 6 is closed to complete the circuit including the winding H and the relay dynamo AB'.

The above described operations are the same when running the dynamo as a motor, but it is necessary to change the sign of the voltage 12b.

The present invention also contemplates the positioning of the relay dynamo AB in the branch p instead of the shunt H. Fig. 6 shows a circuit diagram in which the relay dynamo A'B is positioned in the branch p of the circuit containing the exciting winding H. For passing from series-direct excitation to excitation by the exciting relay, the contactors should be actuated in the same manner as described in connection with Fig. 5.

In installation, where two main dynamos or more than two are operated in series, a relay dynamo according to the present invention can be utilized for exciting both or many of the armatures of said main dynamos as shown in Fig. 7. For passing from series-direct excitation to excitation by the exciting relay, the contactors should be actuated in the same manner as described in connection with Fig. 5.

The present invention is particularly applicable to electric traction. In such application, if the sub-exciter-dynamo 'Ub is driven at a speed proportional to the speed of the wheels of the vehicle and excited with a constant current, a current i is obtained in the main armature, which is approximately proportional to the speed. As a result, the motor or resisting torque of the dynamo XY does not vary much with the speed. Obviously, this is true, provided that the voltage of the relay dynamo can increase suiiiciently for each speed, and the same is true for the voltage else, i. e., the non-attained saturation of the dynamos AB and KY.

In certain instances, it will be convenient to shunt the winding 6 f of the sub-exciter-dynamo m with a self-inductance shown, by way of example, in Fig. 4, as being large with respect to the self-inductance of c Thus, in the rapid transitory working conditions, the excitation of e 1 will increase more rapidly than proportionally to the current i, which will be favorable in the rapid transitory working conditions. The regular Working condition being attained, the current i will divide and pass into L and e f in inverse ratio to their resistances.

It is obvious that a plurality of modifications of the device according to present application are possible.

or course, the respective changes in the connections of the main dynamos during the running as motors can be considered more particularly with the direct series excitation. But in practice a single mode of connections of the dynamos together will be often advantageous in braking running conditions as a generator in order to avoid the difiiculties of the changes of connections when running as generators. But, of course, the changes of connections between dynamos can be made as described when the dynamos are excited in compound semi-direct, as is known.

Lastly, rheostatic braking and subsequently mechanical braking can be employed for stop ping.

I claim:

1. In an electrical circuit, a main dynamo comprising an armature and an exciting field winding, a relay dynamo for exciting the field winding of said main dynamo, said relay dynamo being adapted to operate at a constant speed and comprising an armature, a. field winding for said relay dynamo, means for applying the shunt voltage across said relay dynamo armature to said relay dynamo field winding, means for producing in said relay dynamo field winding 2. regul-atable voltage of the same sign as said shunt voltage for generator operation of the main dynamo and of opposite sign for motor operation of the main dynamo, and means for producing in said relay dynamo field winding a compounding voltage proportional to the current of said main dynamo and of opposite sign to said shunt voltage.

2. In an electric traction system, a main dynamo for driving and braking a vehicle, havin an armature and a field winding, a relay dynamo for exciting the field of said main dynamo and adapted to rotate at constant speed, said relay dynamo comprising an armature, a field winding, means for applying the shunt voltage across said relay dynamo armature to said relay dynamo field winding, a small auxiliary separately excited dynamo adapted to be driven at a speed proportional to that of the main dynamo for imposing a voltage on said relay dynamo.

field winding proportional to the speed of the auxiliary dynamo and of the same sign as the shunt voltage for generator operation of the main dynamo but of opposite sign for motor operation of the main dynamo, and means for producing in said relay dynamo field winding a compounding voltage proportional to the current of said main dynamo and of opposite sign to said shunt voltage.

3. In a traction device, main dynamos each comprising an armature and serially connected series excitation windings, a relay dynamo shunted across one of said series excitation windings, said relay dynamo being adapted to operate at a constant speed and comprising an armature, a field winding for said relay dynamo, means for applying the shunt voltage across said relay dynamo armature to said relay dynamo field winding, means for producing in said relay dynamo field winding a regulatable voltage of the same sign as said shunt voltage for generator operation of the main dynamos and of opposite sign for motor operation of the main dynamos, means for producing in said relay dynamo field winding a compounding voltage proportional to the current of said main dynamos and of opposite sign to said shunt voltage, and means operable for effecting direct series excitation of said main dynamos until started and then effecting compound semi-direct excitation by current generated in said relay dynamos.

4. In a traction device, main dynamos each comprising an armature and serially connected series excitation windings, a relay dynamo shunted across one of said series excitation windings, said relay dynamo being adapted to operate at a constant speed and comprising an armature, a field winding for said relay dynamo, means for applying the shunt voltage across said relay dynamo armature to said relay dynamo field winding, means for producing in said relay dynamo field winding a regulatable voltage of the same sign as said shunt voltage for generator operation of the main dynamos and of opposite sign for motor operation of the main dynamos, means for producing in said relay dynamo field winding a compounding voltage proportional to the current of said main dynamos and of opposite sign to said shunt voltage, and means adapted to be actuated upon changing the coupling between said main dynamos for disconnecting said relay dynamos from said excitation windings and for placing said windings in series direct excitation connection.

5. In an electric circuit, a main dynamo comprising an armature, a series direct excitation winding and a second excitation winding, an exciting relay dynamo having an armature adapted to operate at constant speed, a circuit including said second excitation winding and the armature of said relay dynamo, an exciting coil for said relay dynamo shunted across the armature thereof to receive the shunt voltage of said armature, means for applying an adjustable voltage to said coil to produce ampere-turns therein of the same sign as those produced by the shunt voltage of the relay dynamo armature for generator operation and of opposite sign for motor operation of the main dynamo, means for producing and introducing into said coil a compounding voltage, proportional to the current of the main dynamo, for producing ampere-turns in said coil of a sign opposite to those produced by said shunt voltage during generator operation of the main dynamo,

said means for producing the compounding voltage comprising an auxiliary dynamo having an armature rotating at constant speed, and a field winding excited by current passing through the armature of the main dynamo.

6. In an electric circuit, a main dynamo comprising an armature, a series direct excitation winding and a second excitation winding, an exciting relay dynamo having an armature adapted to operate at constant speed, a circuit including said second excitation winding and the armature of said relay dynamo, an exciting coil for said relay dynamo shunted across the armature thereof to receive the shunt voltage of said armature, means for applying an adjustable voltage to said coil to produce ampere-turns therein of the same sign as those produced by the shunt voltage of the relay dynamo armature for generator operation and of opposite sign for motor operation of the main dynamo, means for producing and introducing into said coil a compounding voltage, proportional to the current of the main dynamo, for producing ampere-turns in said coil of a sign opposite to those produced by said shunt voltage during generator operation of the main dynamo, said means for producing the compounding voltage comprising an auxiliary dynamo having an armature rotating at constant speed, a field winding excited by current passing through the armature of the main dynamo, and a coil of high self-inductance shunted across the field winding of the auxiliary dynamo.

7. In an electric traction system, main dynamos for driving and braking a vehicle, each of said dynamos having an armature, a series direct excitation winding composed of a plurality of separated parts connected in series, means for starting said dynamo with series direct excitation, means for connecting the armature of an exciting relay dynamo in the electric circuit of a part of said series direct excitation winding of any number of main dynamos connected in the same shunt of the network, said exciting relay dynamo having an armature adapted to rotate at a constant speed, an excitation coil for said relay dynamo, means for connecting said 0011 across the armature of said relay dynamo to produce a shunt voltage in said coil, a small auxiliary dynamo separately excited and adapted to operate at a speed proportional to that of the corresponding main dynamo and connected to the excitation coil of the relay dynamo for imposing thereon an adjustable voltage of the same sign as the shunt voltage during generator operation of the main dynamo and of an opposite sign for motor operation of the main dynamo, and means for introducing in the exciting coil of the relay dynamo a compounding voltage proportional to the current of the main dynamo and of a sign opposite to that of said shunt voltage during generator operation of the main dynamo.

8. In an electrical traction system, main dynamos arranged for driving and braking a vehicle, each of said dynamos having an armature, a series direct excitation winding composed of a plurality of separated parts connected in series, means for starting said main dynamos with series direct excitation, means for connecting the armature of an exciting relay dynamo in the electric circuit of a part of the series direct winding of any number of the main dynamos connected in the same shunt of the network, said exciting relay dynamo having an armature adapted to rotate at a constant speed, an excitation coil for the relay dynamo, means for connecting said coil across the armature of said relay dynamo to produce a shunt voltage in said coil, a small auxiliary dynamo separately excited and adapted to be driven at a speed proportional to that of the corresponding main dynamo and connected to the excitation coil of the relay dynamo for imposing thereon a voltage of the same sign as the shunt voltage during the generator operation of the main dynamo and of an opposite sign during motor operation of the main dynamo, means for introducing in the exciting coil of the relay dynamo a compounding voltage proportional to the current of the main dynamo and of a sign opposite to that of said shunt voltage during generator operation of the main dynamo, and means adapted to be operated to eliminate excitation by said relay dynamo and leave only series direct excitation for efiecting change of coupling between dynamos with series direct excitation and after change of coupling has been produced for again effecting excitation by said relay dynamo.

LOUIS RENE EUGENE GRATZMULLER. 

